1. Field of the Invention
The invention relates in general to a de-interlacing device and a method therefor, and more particularly to an edge-based de-interlacing device adapted to motion frames, and a method therefor.
2. Description of the Related Art
A film is generally shot and displayed in an interlaced manner. Taking the television as an example, the displaying of one frame is completed by firstly displaying an odd field thereof and then an even field thereof. The odd field is composed of the odd-numbered lines of the frame, and the even field is composed of the even-numbered lines of the frame.
The typical television has a refresh rate of 30 Hz. That is, 30 frames are displayed in one second. Because the odd and even fields of the frame are alternately displayed, 60 fields are displayed in one second.
The demand on the image quality is getting higher and higher, and the quality of a non-interlaced (i.e., progressive) image is better than that of the interlaced image. Thus, advanced video displaying devices, for example, the high definition television (HDTV), adopt the progressive displaying function.
If the interlaced images are to be displayed in the non-interlaced manner, the interlaced frame has to be de-interlaced and then displayed once in a complete frame. FIG. 1A illustrates an interlaced image including (n−1)th, n-th and (n+1)th fields. In FIG. 1A, pixels having the x coordinates of (i−1) to (i+1) and y coordinates of (j−1) to (j+1) are described as an example. Since each field of the interlaced image only includes odd-numbered or even-numbered horizontal lines to be displayed, only the pixels on the odd-numbered or even-numbered horizontal lines in each field have valid values. In FIG. 1A, the symbol “X” indicates that the pixel in this field has no valid brightness value. De-interlacing the interlaced image is to fill proper brightness values in the pixels having no valid brightness value in each field. Taking the temporal average method as an example, the brightness value of the pixel (i,j) in the n-th non-interlaced frame may be the average of the brightness values of the pixel (i,j) of the interlaced image in the (n−1)th and (n+1)th fields. According to the above-mentioned method, the obtained n-th frame of the non-interlaced image is shown in FIG. 1B.
However, the de-interlacing method mentioned above tends to cause the problem of image flicker. Because the two fields of the interlaced image are shot at different time instants, the image has to be further processed so as to enhance the image quality.